The present invention relates to plasma processing of substrates (or wafers). In particular, the invention relates to controlling ion energy distribution when processing a substrate in a plasma processing system.
Controlling ion energy distribution may provide several benefits in processing the substrate. For example, controlling ion energy distribution may enable the control of etch selectivity between different materials, the reduction of faceting at feature edges (e.g., edges of trenches or vias), and the control of profiles in high aspect-ratio contacts. In modern plasma processing applications, controlling the distribution of ion energy may be critical for achieving desirable processing results. A method for controlling ion energy distribution has been disclosed in U.S. Pat. No. 6,201,208 “Method And Apparatus For Plasma Processing With Control Of Ion Energy Distribution At The Substrates” (issued Mar. 13, 2001), for example.
Prior art techniques for controlling ion energy distribution tend to involve providing a non-sinusoidal radio frequency (RF) signal/power to a substrate-bearing electrode that supports the substrate. This non-sinusoidal signal may control the ion energy distribution, for example, by attracting ions. Prior art techniques for controlling ion energy distribution also tend to require the use of an external DC blocking capacitor between the non-sinusoidal RF signal source and the substrate-hearing electrode.
There are several disadvantages associated with the prior art approaches and given constant advances in the semiconductor processing field, improved techniques and apparatus for controlling ion energy distribution in a plasma processing chamber are desired.